impr: the component supports images embedded in HTML, directly in <img src>, see https://en.wikipedia.org/wiki/Data_URI_scheme
For Delphi XE7 or newer, this feature works automatically.
For older versions of Delphi, this feature requires DIMime and activating {$DEFINE RVUSEDIMIME} in rvHtmlViewImport.pas
(We could implement base64 decoding ourselves, but I do not want to reinvent the wheel)